Whatever excuse you wanna believe, it was a needless and extremely forced plot device that doesn't hold up to logic.

in the context of the film it makes perfect sense

as a film, it means they don't have long sections when there's just one guy grunting or going "almooost" in every fight scene

it allows for character development as they have to work together and get over their shit, giving actual threat if they don't, adding weight to fight scenes to both the characters and, you know, the planet

it makes more sense than say, man of steel, wherein superman doesn't have any reason behind any of his decisions. the people in pacific rim have a reason to fight, a way to fight, and a way to show if it's going well or not, plus actual impact from those